Category: Python

Python : DHT11 : Raspberry ZeroW : No module named ‘board’

I have two Raspberry ZeroW , and I try to use both for to get temperature data. I am recording this data in order to find out when the temperature changes. Both devices should be able to execute the same script. Both have the same hardware setup and they record data on a USB stick.
Kind of weary that on the second device executing the python script fails : I get the error :
No module named ‘board’
That s odd because I am sure the board has been installed.
This is a known issue :
I tried to follow the widely published troubleshooting (reinstalling Blank etc) with no success.
For instance :
pip3 install adafruit-circuitpython-dht
does not work !

The error message ( error: externally-managed-environment ) is followed by a hint which indeed leads me to the solution :
“This environment is externally managed ╰─> To install Python packages system-wide, try apt install … “
The only way to get this issue fixed is installing a virtual environment :

That means :

python3 -m venv ./ws-env
source ws-env/bin/activate
(ws-env) user@raspberrypi:/home/pluto# pip3 install board
(ws-env) user@raspberrypi:/home/pluto# pip3 install adafruit-circuitpython-dht

It works like a charm !

DHT11 / Raspberry Pi Zero W : RuntimeError: Timed out waiting for PulseIn message. Make sure libgpiod is installed…

Took me quite some time to figure out how to get rid of this error, because the Python script for the DHT11 temperature sensor does not get executed. The error message seems to be quite strange because libgpiod is found when executing "pip3 freeze".

The reason for this failure is that libgpiod Python 3 does not work without the installation of libgpiod-dev.

It has to be installed with :

> apt install libgpiod2 libgpiod-dev